Procedure for the treatment of packaged agricultural food products

ABSTRACT

In said procedure, following placement of the agricultural food product in a bag, the following stages are carried out: a) the CO 2  and O 2  are mixed, with the concentration of CO 2  equal to or higher than 40% and the concentration of O 2  equal to or lower than 5%; b) the bag is filled with the mixture resulting from stage (a) by teans of a scavenging operation or the creation of a vacuum inside the bag, setting up a pressure of 350 mbar inside the bag; c) the agricultural food product is exposed to the mixture of gases for a time that ranges between 4 and 26 days, the concentration of CO 2  falling to 30% and the concentration of O 2  rising to 9%; said procedure permitting the eradication of insects and/or mites at any stage of their development.

FIELD OF THE INVENTION

This invention relates to a procedure for the treatment of packagedagricultural food products by means of treating such packagedagricultural food products with a mixture of CO₂/O₂.

This procedure permits eradication of a specific plague of insects andmites independently of the stage of developments those insects and mitesare in.

BACKGROUND OF THE INVENTION

There exist in the state of the art many documents which describe theeffect of CO₂ on insects. (Gerard Nicolas, Daniel Sillans, “Immediateand latent effects of carbon dioxide on insects”, Ann. Rev. Entomol.1989, 34:94-116). The harmful effect of CO₂ on insects is thereforeknown.

Also known is the use of CO₂ to eradicate insects. Indeed, there existmany documents which describe procedures based on the use of carbondioxide, to eradicate insects in agricultural food products (cereals,nuts, etc.).

However, most of these procedures are not effective for all stages ofdevelopment of the insect, so that when agricultural food products arepackaged, the insects reproduce again and a damaged, poor-qualityproduct reaches the consumer.

There nevertheless exist documents in the state of the art whichdescribe packages characterised in that their composition favourseradication with CO₂.

U.S. Pat. No. 6,063,418 relates to a double bag: an inner bag made of aflexible material accommodated within a high-strength outer bag. Owingto CO₂ permeability (lower than 6300 cc/m²·24 h·1 atm) andoxygen-deficiency an insecticidal effect is achieved for several days,it being essential to keep the concentration of CO₂ at 40% for at least7 days.

German patent DE 3832390 relates to a procedure for treating packagedproducts based on a first stage of exposure to vacuum and a second stagein which CO₂ is introduced at a pressure equal to or lower than 12 mbar.

There is nevertheless a need for a procedure for the treatment ofpackaged agricultural food products, based on the use of CO₂, which issimple, using a material (plastic bags) which is affordable (selectedfrom the wide variety of bags that exist for packing agricultural foodproducts) and that is characterised in that the packaged productresulted from the procedure is totally disinfected, with no possibilityof insects in primary stages (such as eggs or larvae) remaining in theproduct.

The object of this invention is therefore a new procedure for thetreatment of packaged agricultural food products that eradicates anyinsect at any stage of development so that the product reaches theconsumer in optimum condition.

DESCRIPTION OF THE INVENTION

This invention relates to a procedure for the treatment of packagedagricultural food products in which, following placement of theagricultural food product in a bag, the following stages are carriedout:

-   -   (a) the gases CO₂ and O₂ are mixed, with the concentration of        CO₂ equal to or exceeding 40% and the concentration of O₂ equal        to or lower than 5%;    -   (b) the bag is filled with the mixture resulting from stage (a)        by means of a scavenging operation or the creation of a vacuum        inside the bag, setting up a pressure of 350 mbar inside the        bag;    -   (c) the agricultural food product is exposed to the mixture of        gases for a time that ranges between 4 and 26 days, in such a        way that the concentration of CO₂ falls to 30% and the        concentration of O₂ rises to 9%.    -   said procedure permitting the eradication of insects and/or        mites at any stage of their development.

In this invention, “scavenging” is taken to mean displacing the airatmosphere inside the bag by introducing a current of the mixture ofgases obtained in stage (a).

In this invention, the term “packaged agricultural food product” refersto a cultivated product or a product made therefrom.

In this invention, “eradication of insects and/or mites at any stage ofdevelopment” means the elimination of insects and/or mites at any of thefollowing stages of development: egg, larva or nymph, pupa and adult.

In this invention, the bag that contains the agricultural food producthas a permeability to O₂ of 30 cm³/m²·24 h·atm and a permeability to CO₂of 150 cm³/m²·24 h·atm at 23° C. and 0% relative humidity.

Another advantageous aspect of this invention is therefore due to thefact that the characteristics of the bag used in the procedure of thisinvention are not restrictive, for this type of bag is affordable and achoice can be made between the large variety of bags for packagingagricultural food products.

As mentioned above, the procedure described in this invention permitsthe eradication of the insects and/or mites associated with the packagedagricultural food product, independently of the stage of development ofsaid insects and/or mites, with the product reaching the consumer in anoptimum condition for consumption and undamaged.

Another advantageous aspect of the procedure of this invention lies inthe fact that the procedure is simple and low in cost, while the type ofbag used for packaging is not an essential aspect for achieving theeradication.

PREFERRED EMBODIMENT OF THE INVENTION

The insects and/or mites used in the trial described below come frombred insects/mites pertaining to all stages of development of eachspecies.

The insectation was carried out in aerated plastic boxes (7.5 cm indiameter by 3 cm high) containing 20 g of the food substrate usednormally for breeding/rearing these pests: PEST BREEDING/REARINGSUSBSTRATE Insects Plodia Interpuctuella Wheat bran + glycerine + beeryeast Tribolium castaneum Flour + beer yeast Sitophilus oryzae RiceAcanthoscelides obtectus Dry kidney beans Lasioderma serricorne Flour +beer yeast Mites Tyrophagus putrescentiae Wheat bran + beer yeast

The boxes containing the insects at their different stages ofdevelopment (eggs, larvae or nymphs, pupae and adults) were placedinside plastic bags (BB4L CRYOVAC) for subsequent creation of vacuum, insuch a way that the concentration of O₂ inside the bag was equal to orlower than 5%.

In order to determine the efficacy of the procedure of the invention,the mixture of gases was made to pass through a saturated salinesolution of potassium chloride. A situation was thus created in whichthe agricultural food product was moist (an adverse situation foreradicating the insects therein).

In brief, a mixture of CO₂ and O₂ gases was prepared using a WITT modelKM 100-3M/MEM mixer. This mixture of gases, which comprised a CO₂concentration higher than or equal to 40% and an O₂ concentration lowerthan or equal to 5% was made to pass through a saturated saline solutionof potassium chloride, following which the mixture of gases wasintroduced into the bag at a pressure of 350 mbar and a sealed vacuumflask time of 1.5 seconds.

Finally, the real concentration of the gases that had entered the bagwas checked by measuring the concentrations of the gases at the baginlet and of the gas inside a test bag, using an ABISS model TOM 12analyser.

Once the mixture of gases had been applied the bags were kept in achamber under controlled conditions (25±1° C., 75±10% relative humidity,photoperiod 16L:8F).

Following the procedure described, it was found that the conditions thatpermitted eradication in an adverse situation such as having a moistagricultural food product, independently of the state of development,for the above-mentioned insects, were preferably: Exposure time (days)P. interpunctella  3-14 T. castaneum  7-14 S. oryzae 10-24 A. obtectus10-30 L. serricorne 10-14 T. putrescentiae  7-14

The exposure time depended on the resistance of each of the pests to thetreatment.

Finally, after allowing an exposure time to elapse (as specified in theabove table for each case), the concentration of CO₂ fell to 30% (wherethe initial concentration had been 40-60%) or to 70% (where the initialconcentration of CO₂ had been 80-99%), while the concentration of O₂rose to 9%.

1. Procedure for the treatment of packaged agricultural food products,wherein following placement of the agricultural food product in a bag,the following stages are carried out: a the CO₂ and O₂ are mixed, withthe concentration of CO₂ being equal to or higher than 40% and theconcentration of O₂ equal to or lower than 5%; b. the bag is filled withthe mixture resulting from stage (a) by means of a scavenging operationor the creation of a vacuum inside the bag, setting up a pressure of 350mbar inside the bag; and c. the agricultural food product is exposed tothe mixture of gases for a time that ranges between 4 and 26 days, insuch a way that the concentration of CO₂ falls to 30% and theconcentration of O₂ rises to 9%. said procedure permitting theeradication of insects and/or mites at any stage of their development 2.Procedure according to claim 1, wherein said bag that contains theagricultural food product has a permeability to O₂ of 30 cm³/m²·24h·atm.
 3. Procedure according to claim 1, wherein said bag has apermeability to CO₂ of 150 cm³/m²·24 h·atm.
 4. Procedure according toclaim 1, wherein said insect is Plodia interpunctella
 5. Procedureaccording to claim 1, wherein said insect is Tribolium castaneum. 6.Procedure according to claim 1, wherein said insect is Sitophylusoryzae.
 7. Procedure according to claim 1, wherein said insect isAcanthoscelides obtectus.
 8. Procedure according to claim 1, whereinsaid insect is Lasioderna seriicornae.
 9. Procedure according to claim1, wherein said mite is Tyrophagus putrescentiae.